[go: up one dir, main page]

US20190378948A1 - Multijunction solar cell with rear-side germanium subcell and the use thereof - Google Patents

Multijunction solar cell with rear-side germanium subcell and the use thereof Download PDF

Info

Publication number
US20190378948A1
US20190378948A1 US16/478,386 US201716478386A US2019378948A1 US 20190378948 A1 US20190378948 A1 US 20190378948A1 US 201716478386 A US201716478386 A US 201716478386A US 2019378948 A1 US2019378948 A1 US 2019378948A1
Authority
US
United States
Prior art keywords
subcell
subcells
solar cell
multijunction solar
germanium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US16/478,386
Other languages
English (en)
Inventor
Frank Dimroth
David Lackner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Assigned to Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. reassignment Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DIMROTH, FRANK, LACKNER, David
Publication of US20190378948A1 publication Critical patent/US20190378948A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/14—Photovoltaic cells having only PN homojunction potential barriers
    • H10F10/142—Photovoltaic cells having only PN homojunction potential barriers comprising multiple PN homojunctions, e.g. tandem cells
    • H01L31/0687—
    • H01L31/02008—
    • H01L31/02021—
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/14—Photovoltaic cells having only PN homojunction potential barriers
    • H10F10/142—Photovoltaic cells having only PN homojunction potential barriers comprising multiple PN homojunctions, e.g. tandem cells
    • H10F10/1425—Inverted metamorphic multi-junction [IMM] photovoltaic cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/16—Photovoltaic cells having only PN heterojunction potential barriers
    • H10F10/161—Photovoltaic cells having only PN heterojunction potential barriers comprising multiple PN heterojunctions, e.g. tandem cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/19—Photovoltaic cells having multiple potential barriers of different types, e.g. tandem cells having both PN and PIN junctions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F19/00—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules
    • H10F19/40—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules comprising photovoltaic cells in a mechanically stacked configuration
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H10F71/127—The active layers comprising only Group III-V materials, e.g. GaAs or InP
    • H10F71/1272—The active layers comprising only Group III-V materials, e.g. GaAs or InP comprising at least three elements, e.g. GaAlAs or InGaAsP
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H10F71/127—The active layers comprising only Group III-V materials, e.g. GaAs or InP
    • H10F71/1276—The active layers comprising only Group III-V materials, e.g. GaAs or InP comprising growth substrates not made of Group III-V materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H10F71/139—Manufacture or treatment of devices covered by this subclass using temporary substrates
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/12—Active materials
    • H10F77/124—Active materials comprising only Group III-V materials, e.g. GaAs
    • H10F77/1248—Active materials comprising only Group III-V materials, e.g. GaAs having three or more elements, e.g. GaAlAs, InGaAs or InGaAsP
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/93—Interconnections
    • H10F77/933—Interconnections for devices having potential barriers
    • H10F77/935—Interconnections for devices having potential barriers for photovoltaic devices or modules
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/95—Circuit arrangements
    • H10F77/953—Circuit arrangements for devices having potential barriers
    • H10F77/955—Circuit arrangements for devices having potential barriers for photovoltaic devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/544—Solar cells from Group III-V materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • FIG. 1 shows four different embodiments according to the invention of the multijunction solar cell (a, b, c, d);
  • FIG. 2 shows diagrams for the band gap and lattice constant for the embodiments according to FIGS. 1 a and 1 b;
  • FIG. 3 shows a detailed layer structure of an embodiment according to the invention.
  • FIG. 4 shows a detailed layer structure of an embodiment according to the invention.
  • Solar cells are used in space for supplying current to satellites. Because of their high efficiency and the high radiation stability compared with silicon, multijunction solar cells made of III-V semiconductors are hereby used predominantly. GaInP/GaInAs/Ge triple solar cells are used as standard, which cells achieve degrees of efficiency of approx. 30% under AMO conditions (i.e. in space) (see G. Strobl, D. Fuhrmann, W. Guter, V. Khorenko, W. Köstler and M. Meusel, About Azur's “3G30-Advanced” space solar cell and next generation product with 35% efficiency in 27 th European Photovoltaic Solar Energy Conference and Exhibition 2012, Frankfurt, Germany, p. 104-108).
  • the solar cells are subjected, in space, to high-energy electrons, protons and other charged particles, which leads to damage to the crystals and a gradual reduction in performance. After radiation with 1 MeV electrons at a flow of 10 15 cm ⁇ 2 , the solar cells typically still have 85 to 90% of their original power. This is also called degree of efficiency at the end of the mission (end-of-life or abbreviated to EOL).
  • a bonded 5-times solar cell was presented by Boeing (P.T. Chiu, D. C. Law, R. L. Woo, S. B. Singer, D. Bhusari, W. D. Hong, A. Zakaria, J. Boisvert, S. Mesropian, R. R. King and N. H. Karam, 35.8% space and 38.8% terrestrial 5J direct bonded cells, 2014 IEEE 40th Photovoltaic Specialists Conference (PVSC), p. 11-13). These solar cells achieve higher degrees of efficiency of 33 to 35% under AMO conditions. The high degrees of efficiency cannot however be obtained unconditionally after irradiation with high-energy particles in space.
  • inverted metamorphic solar cells of Solaero degrade more rapidly than conventional triple solar cells and, after irradiation with 1 MeV electrons at a flow of 10 15 cm ⁇ 3 , achieve similar EOL degrees of efficiency as the triple solar cells based on germanium.
  • EP 3 012 874 A1 relates to a stack-like integrated multijunction solar cell which consists of GaInP/InP/GaInAsP/GalnAs.
  • the GaAs subcell in the inverted metamorphic structure is hereby replaced by a very radiation-stable InP subcell and one of the GaInAs subcells by a radiation-harder GaInAsP subcell.
  • This quadruple solar cell hence has higher radiation stability with, at the same time, higher EOL efficiency.
  • the lowermost GaInAs subcell is still made of a material which has a high degradation under irradiation with high-energy particles.
  • the production of this multijunction solar cell is expensive since the lower layers are produced typically from a substrate based on InP.
  • DE 10 2012 004 734 A1 describes a multijunction solar cell having at least four p-n junctions, in which a lower germanium subcell is connected via a metamorphic buffer to a GaInAs subcell.
  • the GaInAs subcell is in turn connected via a wafer bond to a GaAs—and a GaInP subcell.
  • the uppermost two subcells made of GaInP and GaAs are hereby grown, lattice-adapted, to form GaAs and transferred to the lower structure via wafer bonding.
  • the individual subcells thereby have band gaps of 1.9 eV, 1.4 eV, 1.0 eV and 0.7 eV.
  • This multijunction cell is distinguished by high degrees of efficiency but, under space conditions, has the disadvantage of lower radiation stability of the GaInAs—and GaAs subcells.
  • the plan is to put geostationary satellites firstly into a low Earth orbit and then to convey them by means of ion drive into the GEO orbit.
  • the solar cells are thereby subjected to a very high dose of radiation and solar cells suitable for this application must therefore be designed for radiation doses of >1E16 cm ⁇ 2 .
  • the cells known from the state of the art would, under these conditions, degrade to approx. 60% of their initial power.
  • a multijunction solar cell having at least four p-n junctions which has a rear-side germanium subcell, orientated away from the light, and at least three subcells made of III-V compound semiconductors, disposed above the germanium subcell, at least one metamorphic buffer layer and also a wafer-bonded compound for connecting subcells with a different lattice constant, all of the subcells disposed above the germanium subcell respectively comprising a light-absorbing emitter- and/or base layer, which comprise at least 20% indium, relative to the sum of all the atoms of group III.
  • a subcell made of III-V compound semiconductors within the scope of the present application means that the subcell consists essentially of III-V compound semiconductors, also other atoms being able to be contained up to a proportion of 1%.
  • dopants such as Zn, Se, Mg, C, Si.
  • the subcells disposed above the germanium subcell are abbreviated subsequently with the indices 2 , 2 ′, 2 ′′, 2 ′′′ etc., the subcell directly above the germanium subcell is thereby provided with the index 2 and the subcell disposed above this subcell obtains the index 2 ′ and so on. This numbering is also maintained if intermediate layers, such as metamorphic buffer layers, wafer-bonded compound or tunnel diodes are disposed between the subcells.
  • the percentage proportion of indium, relative to the sum of all the atoms of group III, in the emitter- and/or base layer of the subcell 2 ′ and all of the subcells 2 ′′, 2 ′′′, . . . disposed above the subcell 2 ′ is at least 40% and preferably at least 45%.
  • the percentage proportion of indium, relative to the sum of all the atoms of group III, in the emitter- and/or base layer of the subcell 2 ′ is at least 60% and preferably at least 70%.
  • the percentage proportion of phosphorus, relative to the sum of all the atoms of group V (group V means the 5 th main group of the periodic table of elements, i.e. N, P, As, Sb and Bi), in the emitter- and/or base layer of the subcells 2 and 2 ′ disposed above the germanium subcell, is at least 5%, preferably at least 15%.
  • the percentage proportion of phosphorus, relative to the sum of all the atoms of group V, in the emitter- and/or base layers of the subcells 2 ′, 2 ′′, 2 ′′′, . . . disposed above the subcell 2 is at least 50%, preferably at least 80%.
  • the thickness of the III-V subcells is 400 to 4,000 nm.
  • the germanium subcell has a p-doped base layer made of germanium with a band gap of 0.67 eV at 300 K.
  • Another preferred embodiment of the present invention provides that the lattice constant of the germanium subcell is 5.658 angstrom.
  • the germanium subcell has a thickness of more than 4 ⁇ m, preferably more than 60 ⁇ m.
  • Germanium is very well suited as material for the rear-side subcell since, in comparison to other substrates, such as e.g. InP, it incurs lower costs and a p-n junction can be produced by diffusion, which makes it possible to absorb photons in the infrared range with an energy greater than the band gap of 0.67 eV and to convert them into electrical current.
  • germanium solar cells have a very high radiation stability in space.
  • the germanium subcell has a metal contact on the side orientated away from the light.
  • Another preferred embodiment of the present invention provides that, between the germanium subcell and the subcell 2 , a metamorphic buffer layer is disposed. This converts the lattice constant of the germanium subcell into the lattice constant of the subcell 2 , the lattice constant of the subcell 2 being preferably 5.75 to 5.90 angstrom and particularly preferably from 5.77 to 5.85 angstrom.
  • the metamorphic buffer layer can have a constant gradient in the lattice constant, or the lattice constant can be increased rapidly within the metamorphic buffer layer in steps, in this case, mismatching dislocations forming preferably at the places at which the lattice constant is increased in steps.
  • the gradient in the lattice constant is achieved by a gradual change in composition in layers made of III-V compound semiconductors, such as AlGaInAsP, AlGaInP, GaInP, AlGaInAs, GaAsSb or GaInAs or GaInAsN, which can be n- or p-doped and which can comprise further elements such as N or B, in order to increase the crystal hardness.
  • the lattice constant within the layer can also be increased beyond the target lattice constant.
  • the aim is to adjust the lattice constant of the subsequent subcell 2 ′ at the end of the metamorphic buffer layer 3 in the plane and to ensure a low density of thread- or piercing dislocations.
  • the subcell 2 and the subcell 2 ′ are lattice-adapted to each other.
  • the subcells 2 , 2 ′ have a lattice constant of 5.75 to 5.90 angstrom and particularly preferably of 5.77 to 5.85 angstrom.
  • an electrically conductive wafer-bonded compound which preferably has a resistance of at most 5 ohm cm 2 , particularly preferably of at most 500 mohm cm 2 .
  • the wafer bond forms a flush-mounted electrically conductive, optically transparent and mechanically stable compound between the subcells 2 ′ and 2 ′′. This can be effected by a direct wafer bonding with covalent bonds between the semiconductor surfaces or by suitable intermediate layers, such as transparent, conductive oxides, amorphous semiconductors or suitable conductive adhesives.
  • a further preferred embodiment according to the invention provides that the emitter- and/or base layer of the front-side subcell, orientated towards the light, consists of AlGaInP and has a band gap energy of preferably 1.8 to 2.1 eV, particularly preferably 1.85 to 2.0 eV.
  • the front-side subcell is preferably lattice-adapted to GaAs or germanium.
  • a preferred multijunction solar cell consists of four subcells 1 , 2 , 2 ′, 2 ′′, the emitter- and/or base layer of the subcell 2 consisting of GaInAsP, the emitter- and/or base layer of the subcell 2 ′ of GaInP and the emitter- and/or base layer of the subcell 2 ′′ of AlGaInP.
  • Another multijunction solar cell consists of five subcells 1 , 2 , 2 ′, 2 ′′, 2 ′′′, the emitter- and/or base layers of the subcells 2 , 2 ′ consisting of GaInAsP, the emitter- and/or base layer of the subcell 2 ′′ of AlGaInAsP and the emitter- and/or base layer of the subcell 2 ′′ of AlGaInP.
  • the metamorphic buffer layer between the germanium subcell 1 and the subcell 2 reflects at least 30%, in particular 70%, of the radiation in the absorption range of the subcell 2 .
  • tunnel diodes which connect the subcells serially are disposed between the subcells 1 , 2 , 2 ′, 2 ′′, 2 ′′′, . . . .
  • a further preferred embodiment according to the invention provides that the power of the multijunction solar cell after irradiation with 1 MeV electrons with a flow of 10 16 cm ⁇ 2 degrades by less than 35%, preferably by less than 20%.
  • the multijunction solar cells according to the invention are used preferably in space and are used in particular for satellites.
  • FIG. 1 a shows a preferred structure of a multijunction solar cell according to the invention with 4 subcells which have respectively an emitter and base layer and also a p-n junction.
  • said multijunction solar cell comprises, from bottom to top, a germanium subcell 1 , a metamorphic buffer layer 3 , a GaInAsP subcell 2 , an InP subcell 2 ′, a wafer-bonded compound 4 and also a GaInP subcell 2 ′′.
  • the growth of the subcells 2 and 2 ′′ can be effected in the same epitaxial process in which the metamorphic buffer layer 3 is also deposited. Alternatively, firstly only the metamorphic buffer layer 3 is deposited and the surface is then polished in a separate process in order to reduce the roughness before, in a further epitaxial process, the subcells 2 and 2 ′′ are deposited.
  • a fourth GaInP subcell 2 ′′ with a band gap energy of 1.88 eV, is grown, lattice-adapted, on GaAs (5.653 angstrom) or germanium (5.658 angstrom) and subsequently is transferred to the lower structure via wafer bonding and substrate removal.
  • All subcells 2 , 2 ′, 2 ′′ have respectively an emitter and a base layer, a p-n junction being formed between the emitter and the base layer. If the emitter layer has an n-doping, then the base layer is p-doped and vice versa. Typical n-dopants comprise Si, Se, Te and p-dopants Zn, Mg and C. If emitter and base layer have the same band gap energy, then it is called a homo-solar cell, whereas if the emitter has a lower or higher band gap, compared to the base, then it is called a hetero-solar cell.
  • the subcells 2 , 2 ′, 2 ′′ can be configured both as homo-, and as hetero-solar cell.
  • the resulting multijunction solar cell structure comprises four subcells 1 , 2 , 2 ′, 2 ′′, with respectively one p-n junction, the materials for the emitter and/or base layer of the subcells (GaInP, InP, GaInAsP and Ge) having a high resistance relative to particle radiation in space.
  • FIG. 1 b shows a further preferred structure of a multijunction solar cell according to the invention.
  • said multijunction solar cell comprises, from bottom to top, a germanium subcell 1 , a metamorphic buffer layer 3 , a GaInAsP subcell 2 , a GaInP subcell 2 ′, a wafer-bonded compound 4 and also an AlGaInP subcell 2 ′′.
  • the metamorphic buffer layer 3 is converted from a lattice constant of 5.658 angstrom to a lattice constant of 5.75 to 5.90, in particular 5.80 to 5.87 angstrom (see right-hand part of FIG. 2 , the lattice constants are taken from the loffe data bank: “http://www.ioffe.ru/SVA/NSM/Semicond”).
  • the desired band gaps for the second and third subcell can likewise be achieved by compositions of GaInAsP 2 or GaInP 2 ′ with high radiation stability.
  • FIG. 1 c Another preferred structure of a multijunction solar cell according to the present invention is shown in FIG. 1 c.
  • said multijunction solar cell comprises, from bottom to top, a germanium subcell 1 , a metamorphic buffer layer 3 , two GaInAsP subcells 2 , 2 ′, a wafer-bonded compound 4 , a fourth AlGaInAsP subcell 2 ′′ and also a fifth AlGaInP subcell 2 ′′′.
  • the first two subcells 2 , 2 ′ are thereby produced on the metamorphic buffer layer 3 and the uppermost two subcells are lattice-adapted to a GaAs or Ge substrate.
  • the uppermost two subcells are in turn transferred by means of wafer-bonding and substrate removal onto the lower part of the solar cell structure.
  • FIG. 1 d A further preferred structure of a multijunction solar cell according to the present invention is shown in FIG. 1 d.
  • said multijunction solar cell comprises, from bottom to top, a germanium subcell 1 , a metamorphic buffer layer 3 , two GaInAsP subcells 2 , 2 ′, an AlGaInAsP subcell 2 ′′, a wafer-bonded compound 4 and also a fifth AlGaInP subcell 2 ′′.
  • the first three subcells 2 , 2 ′, 2 ′′ are thereby produced on the metamorphic buffer layer 3 and the uppermost subcell is grown, lattice-adapted, on GaAs or Ge substrate and subsequently transferred by means of wafer-bonding and substrate removal to the lower subcells 1 , 2 , 2 ′, 2 ′′.
  • a p-n junction is produced in p-germanium by diffusion of arsenic or phosphorus from the gas phase.
  • a nucleation layer made of n-doped GaAs or GaInP is deposited, lattice-adapted. This layer serves as front-side passivation for the first germanium subcell.
  • a metamorphic buffer layer made of GaInP or AlGaInAsP is deposited, in which the lattice constant of 5.658 angstrom for Ge is converted to a lattice constant of 5.75 to 5.90, in particular 5.80 to 5.87 angstrom.
  • the lattice constant is increased continuously (e.g. linearly) or in steps, mismatching dislocations being formed and stress-relieving the crystal.
  • the metamorphic buffer is configured such that at the end a stress-relieved crystal lattice with the target lattice constant and an as small as possible piercing dislocation density is present.
  • the buffer can be configured optionally as Bragg mirror in order to reflect non-absorbed photons into the subcell situated above.
  • a tunnel diode is grown which serves to connect the subcells serially.
  • the tunnel diode consists of degenerate n- and p-doped semiconductor layers, such as e.g. p-AlGaAs and n-GaInAs, and can optionally be surrounded by higher band gap barrier layers.
  • n- and p-doped semiconductor layers such as e.g. p-AlGaAs and n-GaInAs
  • a second In-containing subcell made of GaInAsP with a band gap energy of approx. 1.03 eV is deposited.
  • a possible composition of the structure according to the left-hand side of FIG. 1 is Ga 0.21 In 0.79 As 0.45 P 0.55 , lattice-adapted to InP with a band gap energy of 1.03 eV.
  • the GaInAsP absorber layer can hereby form the n-doped or the p-doped or both regions of the subcell, the doping being achieved by addition of typical doping atoms, such as Si, Se, Te, C, Mg, Zn in a concentration range of 1E16-3E18 cm ⁇ 3 .
  • the solar cell has, furthermore, barrier layers on the front- and rear-side with a higher band gap energy in order to conduct minority charge carriers to the p-n junction. For example, a p-AlGaInAs rear-side barrier and an n-AlInP front-side barrier is used.
  • a further tunnel diode is connected, which is formed for example from p-AlGaAsSb and n-GaInP.
  • the composition of the semiconductor layers is either lattice-adapted to the 2 nd subcell situated therebelow or the compressive strain of a layer is compensated for by the tension strain of an adjacent layer. This “strain balancing” functions in layers which are not stress-relieved because of too little thickness. It is essential that the average lattice constant corresponds to that of the 1 st subcell.
  • a third In-containing subcell made of GaInP with a band gap energy of 1.35 eV is deposited, the GaInP layer in turn forming the n-doped emitter, the p-doped base or both and dopants, such as Si, Se, Te, C, Mg, Zn, being used in a concentration range of 1E16-3E18 cm ⁇ 3 .
  • a possible composition of the structure according to the left-hand part of FIG. 1 is InP.
  • the third subcell is lattice-adapted to the second subcell. Above the third subcell, an AlGaInAsP-bonded layer, preferably with a high n-doping in the range of 1E19-5E19 cm ⁇ 3 is applied.
  • This layer serves as front-side barrier for the 3 rd subcell and as connection to the 4 th subcell.
  • the bonded layer is intended to have as low absorption as possible.
  • n-AlGaInAsP is used and, before the wafer bonding, is machined by means of chemical-mechanical polishing in order to ensure low surface roughness.
  • a 4 th upper cell made of (Al)GaInP with a band gap energy between 1.8 to 2.1 eV is bonded, which was grown epitaxially separately and lattice-adapted on GaAs or Ge.
  • the wafer bond bridges the difference in the lattice constant of the third (5.75 to 5.90, in particular 5.80 to 5.87 angstrom) and fourth cell (GaAs 5.653 angstrom or germanium 5.658 angstrom).
  • the epitaxial structure of the uppermost partial layer has in turn a highly doped n-AlGaInP-bonded layer with low roughness which is connected for example via a direct surface-activated wafer bond to the n-AlGaInAsP-bonded layer of the lower cell structure.
  • the surface activation can be effected for example by bombarding with argon atoms in a high vacuum, as a result of which a thin amorphous bonded layer of a few nm is formed at the interface.
  • the bond between the uppermost GaInP subcell and the third In-containing subcell can be effected by transparent conductive oxides or by other conductive adhesive compounds which have the necessary property of mechanical stability, optical transparency and electrical conductivity.
  • a further tunnel diode is connected made of degenerate n- and p-doped semiconductor layers, such as e.g. p-AlGaAs and n-GaInP.
  • the average lattice constant corresponds to that of the 4 th subcell which consists of AlGaInP with a band gap energy of 1.88 eV.
  • the AlGaInP absorber layer can in turn form the n-doped or the p-doped or both regions of the subcell, the doping being achieved by addition of typical doping atoms, such as Si, Se, Te, C, Mg, Zn, in a concentration range of 1E16-3E18 cm ⁇ 3 .
  • the semiconductor structure ends on the side, orientated towards the light, with an AlInP window layer as barrier and a GaInAs contact layer.
  • the production of the multijunction solar cell is effected by means of epitaxial growth (preferably organometallic gas phase epitaxy) of two separate structures.
  • the lower part of the multijunction solar cell up to the n-AlGaInAsP-bonded layer is grown epitaxially on a Ge substrate, the lattice constant being increased through the metamorphic buffer from 5.658 angstrom to 5.75 to 5.90, in particular 5.80 to 5.87 angstrom, for the 2 nd and 3 rd subcell.
  • the uppermost 4 th AlGaInP subcell is grown epitaxially, in a separate epitaxial process for example lattice-adapted, in inverted layer sequence, on GaAs 5.653 angstrom or germanium 5.658 angstrom.
  • the two layer sequences of the subcells 1 to 3 are connected by means of wafer-bonding to that of the 4 th subcell and the growth substrate made of GaAs or Ge on the 4 th subcell is removed.
  • This can be effected for example via a lift-off process (chemically, via a laser process or by mechanical tension), via mechanical grinding or by wet-chemical etching processes.
  • the processing of the multijunction solar cell comprises further steps for the production of metal contacts on the front- and rear-side and also the removal of the GaAs contact layer between the metal fingers on the front-side.
  • Another antireflection coating is applied here also, which consists for example of two layers made of titanium oxide and aluminium oxide. Other materials for the antireflection coating comprise for example tantalum oxide, silicon nitride or magnesium fluoride.
  • the multijunction solar cell structure according to FIG. 1 b is configured just like the structure according to FIG. 1 a, only a higher band gap energy for the uppermost AlGaInP subcell is set and the lattice constant of the 2 nd and 3 rd subcell is adapted by composition changes in GaInAsP and GaInP such that an as thin as possible metamorphic buffer with the smallest possible gradient in the lattice constant can be used. This reduces damaging piercing dislocations and is economically attractive since less semiconductor material need be deposited. Furthermore it is advantageous to convert the structure not entirely to the lattice constant of InP since then higher barriers for minority charge carriers on the front- and rear-side of the 3 rd subcell are possible.
  • the multijunction solar cell structure according to FIGS. 1 c and d is a further development of the structures in FIGS. 1 a and b, here 5 subcells made of AlGaInP/AlGaInAsP/GaInAsP/GaInAsP/Ge being used.
  • the first three or four subcells are in turn grown epitaxially on germanium and comprise a metamorphic buffer between the Ge lower cell and the GaInAsP subcell.
  • the band gaps of the materials are chosen such that they are close to the theoretical optimum of 2.15, 1.6, 1.21, 0.9, 0.64 eV.
  • the uppermost subcell or the uppermost two subcells made of AlGaInP and AlGaInAsP are grown epitaxially, lattice-adapted, on GaAs or Ge and then bonded to the lower cell structure.
  • a multijunction solar cell which can achieve an even higher efficiency in space under AMO conditions is produced and which uses, at the same time, only In-containing subcells with a high radiation hardness.
  • the examples shown here can also be extended by a further sixth subcell, as a result of which even higher AMO degrees of efficiency are theoretically possible.
  • the band gaps and layer thicknesses of the subcells are adapted such that as high as possible a conversion efficiency of the multijunction solar cell after radiation in space is achieved.

Landscapes

  • Photovoltaic Devices (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Sustainable Energy (AREA)
  • Sustainable Development (AREA)
US16/478,386 2017-01-18 2017-12-19 Multijunction solar cell with rear-side germanium subcell and the use thereof Abandoned US20190378948A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE102017200700.1A DE102017200700A1 (de) 2017-01-18 2017-01-18 Mehrfachsolarzelle mit rückseitiger Germanium-Teilzelle und deren Verwendung
DE102017200700.1 2017-01-18
PCT/EP2017/083570 WO2018134016A1 (de) 2017-01-18 2017-12-19 Mehrfachsolarzelle mit rückseitiger germanium-teilzelle und deren verwendung

Publications (1)

Publication Number Publication Date
US20190378948A1 true US20190378948A1 (en) 2019-12-12

Family

ID=60953832

Family Applications (1)

Application Number Title Priority Date Filing Date
US16/478,386 Abandoned US20190378948A1 (en) 2017-01-18 2017-12-19 Multijunction solar cell with rear-side germanium subcell and the use thereof

Country Status (4)

Country Link
US (1) US20190378948A1 (de)
EP (1) EP3571725A1 (de)
DE (1) DE102017200700A1 (de)
WO (1) WO2018134016A1 (de)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112635608A (zh) * 2020-12-21 2021-04-09 中国电子科技集团公司第十八研究所 一种锗基晶格失配四结太阳电池
US11127873B2 (en) 2019-09-27 2021-09-21 Azur Space Solar Power Gmbh Monolithic multijunction solar cell having exactly four subcells
EP3937260A1 (de) * 2020-07-10 2022-01-12 AZUR SPACE Solar Power GmbH Monolithische metamorphe mehrfachsolarzelle
US11374140B2 (en) 2020-07-10 2022-06-28 Azur Space Solar Power Gmbh Monolithic metamorphic multi-junction solar cell
US11563133B1 (en) 2015-08-17 2023-01-24 SolAero Techologies Corp. Method of fabricating multijunction solar cells for space applications
US11588067B2 (en) 2020-07-10 2023-02-21 Azur Space Solar Power Gmbh Monolithic metamorphic multi-junction solar cell
US11652182B2 (en) 2016-10-14 2023-05-16 Solaero Technologies Corp. Five junction multijunction metamorphic solar cell
US20230207717A1 (en) * 2016-10-14 2023-06-29 Solaero Technologies Corp. Multijunction metamorphic solar cells
CN119421501A (zh) * 2025-01-02 2025-02-11 南昌凯捷半导体科技有限公司 一种三结太阳电池及其制备方法
US12249667B2 (en) 2017-08-18 2025-03-11 Solaero Technologies Corp. Space vehicles including multijunction metamorphic solar cells
US12501736B2 (en) 2021-12-07 2025-12-16 Solaero Technologies Corp Method of fabricating metamorphic multijunction solar cells for space applications

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6316715B1 (en) * 2000-03-15 2001-11-13 The Boeing Company Multijunction photovoltaic cell with thin 1st (top) subcell and thick 2nd subcell of same or similar semiconductor material
DE102005000767A1 (de) * 2005-01-04 2006-07-20 Rwe Space Solar Power Gmbh Monolithische Mehrfach-Solarzelle
WO2012154675A1 (en) * 2011-05-06 2012-11-15 Alliance For Sustainable Energy, Llc Photovoltaic device
DE102012004734A1 (de) 2012-03-08 2013-09-12 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Mehrfachsolarzelle und deren Verwendung
US9035367B2 (en) * 2013-10-11 2015-05-19 Solaero Technologies Corp. Method for manufacturing inverted metamorphic multijunction solar cells
DE102014210753B4 (de) * 2014-06-05 2017-04-27 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Halbleiterbauelement auf Basis von In(AlGa)As und dessen Verwendung
EP2960950B1 (de) * 2014-06-26 2023-01-25 AZUR SPACE Solar Power GmbH Mehrfach-solarzelle
EP2991124A1 (de) * 2014-08-29 2016-03-02 AZUR SPACE Solar Power GmbH Stapelförmige integrierte Mehrfachsolarzelle und Verfahren zur Herstellung einer stapelförmigen integrierten Mehrfachsolarzelle
EP3012874B1 (de) 2014-10-23 2023-12-20 AZUR SPACE Solar Power GmbH Stapelförmige integrierte Mehrfachsolarzelle

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11563133B1 (en) 2015-08-17 2023-01-24 SolAero Techologies Corp. Method of fabricating multijunction solar cells for space applications
US11652182B2 (en) 2016-10-14 2023-05-16 Solaero Technologies Corp. Five junction multijunction metamorphic solar cell
US20230207717A1 (en) * 2016-10-14 2023-06-29 Solaero Technologies Corp. Multijunction metamorphic solar cells
US11721777B1 (en) 2016-10-14 2023-08-08 Solaero Technologies Corp. Multijunction metamorphic solar cell
US12249667B2 (en) 2017-08-18 2025-03-11 Solaero Technologies Corp. Space vehicles including multijunction metamorphic solar cells
US11127873B2 (en) 2019-09-27 2021-09-21 Azur Space Solar Power Gmbh Monolithic multijunction solar cell having exactly four subcells
EP3937260A1 (de) * 2020-07-10 2022-01-12 AZUR SPACE Solar Power GmbH Monolithische metamorphe mehrfachsolarzelle
US11374140B2 (en) 2020-07-10 2022-06-28 Azur Space Solar Power Gmbh Monolithic metamorphic multi-junction solar cell
US11588067B2 (en) 2020-07-10 2023-02-21 Azur Space Solar Power Gmbh Monolithic metamorphic multi-junction solar cell
CN112635608A (zh) * 2020-12-21 2021-04-09 中国电子科技集团公司第十八研究所 一种锗基晶格失配四结太阳电池
US12501736B2 (en) 2021-12-07 2025-12-16 Solaero Technologies Corp Method of fabricating metamorphic multijunction solar cells for space applications
CN119421501A (zh) * 2025-01-02 2025-02-11 南昌凯捷半导体科技有限公司 一种三结太阳电池及其制备方法

Also Published As

Publication number Publication date
EP3571725A1 (de) 2019-11-27
DE102017200700A1 (de) 2018-07-19
WO2018134016A1 (de) 2018-07-26

Similar Documents

Publication Publication Date Title
US20190378948A1 (en) Multijunction solar cell with rear-side germanium subcell and the use thereof
US20240379889A1 (en) Group-iv solar cell structure using group-iv heterostructures
Feifel et al. Epitaxial GaInP/GaAs/Si triple‐junction solar cell with 25.9% AM1. 5g efficiency enabled by transparent metamorphic AlxGa1− xAsyP1− y step‐graded buffer structures
Guter et al. Space solar cells–3G30 and next generation radiation hard products
US8822817B2 (en) Direct wafer bonding
Cariou et al. Monolithic two-terminal III–V//Si triple-junction solar cells with 30.2% efficiency under 1-sun AM1. 5g
US10263129B2 (en) Multijunction photovoltaic device having SiGe(Sn) and (In)GaAsNBi cells
Jain et al. III–V multijunction solar cell integration with silicon: Present status, challenges and future outlook
US20150053257A1 (en) Multi-junction solar cell and use thereof
US11211510B2 (en) Multijunction solar cell with bonded transparent conductive interlayer
US11646388B2 (en) Group-IV solar cell structure using group-IV or III-V heterostructures
CN102422443B (zh) 由应力补偿化合物半导体层构成的隧道二极管
US9997659B2 (en) Group-IV solar cell structure using group-IV or III-V heterostructures
US10896990B2 (en) Group-IV solar cell structure using group-IV or III-V heterostructures
Pakhanov et al. State-of-the-art architectures and technologies of high-efficiency solar cells based on III–V heterostructures for space and terrestrial applications
JP2014123712A (ja) 太陽電池の製造方法
US20120138130A1 (en) Tunnel diodes comprising stress-compensated compound semiconductor layers
TWI775725B (zh) 用於半導體裝置的基於銻化物的高能帶間隙穿隧式接面
Miyashita et al. Inverted lattice-matched triple junction solar cells with 1.0 eV GaInNAsSb subcell by MOCVD/MBE hybrid growth
US10026856B2 (en) Systems and methods for advanced ultra-high-performance InP solar cells
Lackner et al. Status of four-junction cell development at fraunhofer ISE
US20150372179A1 (en) Multi-junction solar cell, methods for the production thereof, and uses thereof
JP2014057095A (ja) 光電変換装置
US9040342B2 (en) Photovoltaic cell and manufacturing method thereof
Dimroth III‐V Solar Cells–Materials, Multi‐Junction Cells–Cell Design and Performance

Legal Events

Date Code Title Description
AS Assignment

Owner name: FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:DIMROTH, FRANK;LACKNER, DAVID;SIGNING DATES FROM 20190910 TO 20190911;REEL/FRAME:050404/0610

STPP Information on status: patent application and granting procedure in general

Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER

STPP Information on status: patent application and granting procedure in general

Free format text: FINAL REJECTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: RESPONSE AFTER FINAL ACTION FORWARDED TO EXAMINER

STPP Information on status: patent application and granting procedure in general

Free format text: ADVISORY ACTION MAILED

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION